Apparatus for fabrication of three dimensional objects

1. An apparatus for bottom-up fabrication of three dimensional objects, the apparatus comprising: a vat for a photosensitive polymer, a floor of the vat including a working surface arranged such that, in use, light incident on the working surface interacts with the photosensitive polymer at the working surface to fabricate a portion of the three dimensional object; a build platform configured to be inserted into the vat, the build platform having a planar surface; an elevator mechanism configured to adjust a separation between the working surface of the vat and the planar surface of the build platform; and a rotation mechanism configured to vary a relative rotational position of the vat relative to the build platform, the relative rotational position being about an axis which is normal to the working surface of the vat; wherein the floor includes a first floor portion of a first thickness and a second floor portion of a second thickness, the second thickness being less than the first thickness; wherein the first floor portion has a first vertical side, the second floor portion has a second vertical side, and the first vertical side directly contacts the second vertical side, and wherein the rotation mechanism is configured to vary the relative rotational position about the axis between a first position and a second position, the first position locating the first floor portion under the planar surface of the build platform to fabricate the portion of the three dimensional object at the working surface, and the second position locating the second floor portion under the planar surface to increase a depth of the photosensitive polymer between the portion of the three dimensional object and the floor of the vat.

2. The apparatus of claim 1 , wherein the rotation mechanism is arranged to vary the rotational position of the vat.

3. The apparatus of claim 2 , wherein the rotation mechanism is a rotatable plate upon which the vat is mounted.

4. The apparatus of claim 3 , wherein the vat includes a plug and the rotatable plate includes an aperture, the plug being configured to engage the aperture to secure the vat to the rotatable plate.

5. The apparatus of claim 1 , wherein the rotation mechanism is arranged to vary the rotational position of the build platform.

6. The apparatus of claim 1 further comprising a heating element in thermal contact with the vat.

7. The apparatus of claim 1 wherein the floor of the vat has a thickness of at least 5 mm.

8. The apparatus of claim 1 , wherein the first floor portion has a thickness of at least 6 mm and the second floor portion has a thickness of at least 5 mm.

9. The apparatus of claim 1 wherein the vat is formed entirely of a liquid silicone rubber.

10. The apparatus of claim 1 , wherein the vat is made of optically clear material comprising a thermoplastic and is not made entirely of a liquid silicone rubber, and the first floor portion comprises a replaceable optically clear silicone pad comprising the first vertical side and the working surface.

11. An apparatus for bottom-up fabrication of three dimensional objects, the apparatus comprising: a vat for a photosensitive polymer, a floor of the vat including a working surface arranged such that, in use, light incident on the working surface interacts with the photosensitive polymer at the working surface to fabricate a portion of the three dimensional object; a build platform configured to be inserted into the vat, the build platform having a planar surface; an elevator mechanism configured to adjust a separation between the working surface of the vat and the planar surface of the build platform; and a rotation mechanism configured to vary a relative rotational position of the vat relative to the build platform, the relative rotational position being about an axis which is normal to the working surface of the vat; wherein the floor includes a first floor portion of a first thickness and a second floor portion of a second thickness, the second thickness being less than the first thickness; and wherein the rotation mechanism is configured to vary the relative rotational position about the axis between a first position and a second position, the first position locating the first floor portion under the planar surface of the build platform to fabricate the portion of the three dimensional object at the working surface, and the second position locating the second floor portion under the planar surface to increase a depth of the photosensitive polymer between the portion of the three dimensional object and the floor of the vat.

12. The apparatus of claim 11 , wherein the rotation mechanism is arranged to vary the relative rotational position of the vat.

13. The apparatus of claim 12 , wherein the rotation mechanism is a rotatable plate upon which the vat is mounted.

14. The apparatus of claim 13 , wherein the vat includes a plug and the rotatable plate includes an aperture, the plug being configured to engage the aperture to secure the vat to the rotatable plate.

15. The apparatus of claim 11 , wherein the rotation mechanism is arranged to vary the rotational position of the build platform.

16. The apparatus of claim 11 , further comprising a heating element in thermal contact with the vat.

17. The apparatus of claim 11 , wherein the floor of the vat has a thickness of at least 5 mm.

18. The apparatus of claim 11 , wherein the first floor portion has a thickness of at least 6 mm and the second floor portion has a thickness of at least 5 mm.

19. The apparatus of claim 11 , wherein the vat is formed entirely of a liquid silicone rubber.

20. The apparatus of claim 11 , wherein the vat is made of optically clear material comprising a thermoplastic and is not made entirely of a liquid silicone rubber, and the first floor portion comprises a replaceable optically clear silicone pad comprising the working surface.